S-Triazine as an exchange linker in organic high-spin molecules

Abstract

s-Triazine was used as an exchange linker to couple phenyl- t-butylnitroxide and t-butylated phenoxyl radicals. Quartet and triplet state systems of both types were identified by ESR spectroscopy. The quartet state zero field splittings of 2,4,6-tris(4- N- t-butyl- N-aminoxylphenyl)- s-triazine ( 1) and 2,4,6-tris(3,5-di- t-butyl-4-oxyphenyl)- s-triazine ( 2) were | D|=12 and 33 G, respectively. The phenoxyl-based systems were persistent in solution, but not solid state stable. The s-triazine unit accommodates planarity of attached phenyl rings in the solid state, as shown by crystallographic studies of 1 and phenolic precursors to the phenoxyl-based systems. Triradical ( 1) was subjected to magnetic analysis by an equilateral triangular model with mean field inter-radical interactions, giving J intra/ k B=+9.0 K and J inter/ k B=−1.45 K. A similar isosceles triangle model gave J 1-intra/ k B=+10.5 K, J 2-intra/ J 1-intra=0.77 and J inter/ k B=−1.3 K. Compound 1 thus has a ferromagnetically coupled quartet ground state, with a small AFM coupling between molecules.